An off-line power supply circuitry may receive electrical power from an alternating-current (AC) main supply (e.g., an electrical grid) and convert it to a lower direct-current (DC) voltage suitable to power an electrical load. An off-line power supply may include safety isolation between the input side (e.g., primary-side circuitry) and the output side (e.g., secondary-side circuitry). The regulating element of the power supply (e.g., the primary controller) may be on the primary side, but the regulated parameter (e.g., the output DC voltage) may be available only on the secondary side.
Therefore, the power supply circuitry may include some kind of communication media to send information from the secondary side to primary side. The power supply circuitry may include an optocoupler for this purpose, but some other devices like capacitive- or transformer-based couplers are gaining popularity. For many types of device for sending information, the signal may pass through the safety isolation, which may increase the system cost, may consume take space, and may reduce system reliability.